2008.11.30 原程序: #include <fcntl.h> #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <time.h> int main() { int fds[2]; char buf[100]; int i,rc,maxfd; fd_set inset1,inset2; struct timeval tv; if((fds[0] = open("hello1",O_RDWR | O_CREAT,0666))<0) perror("open hello1"); if((fds[1] = open("hello2",O_RDWR | O_CREAT,0666))<0) perror("open hello2"); if((rc=write(fds[0],"hello!\n",7))) printf("rc=%d\n",rc); lseek(fds[0],0,SEEK_SET); maxfd = fds[0]>fds[1] ? fds[0] : fds[1]; FD_ZERO(&inset1); FD_SET(fds[0],&inset1); FD_ZERO(&inset2); FD_SET(fds[1],&inset2); tv.tv_sec=2; tv.tv_usec=0; while(FD_ISSET(fds[0],&inset1) || FD_ISSET(fds[1],&inset2)) { if(select(maxfd+1,&inset1,&inset2,NULL,&tv)<0) perror("select"); else { if(FD_ISSET(fds[0],&inset1)) { rc= read(fds[0],buf,7); if(rc>0) { buf[rc]='\0'; printf("read: %s\n",buf); } else perror("read"); } if(FD_ISSET(fds[1],&inset2)) { rc=write(fds[1],buf,7); if(rc>0) { buf[rc]='\0'; printf("rc=%d,write:%s\n",rc,buf); } else perror("write"); sleep(10); } }
} exit(0); }
运行结果:
[root@localhost exp]# ./select rc=7 read: hello!
rc=7,write:hello!
read: Success rc=7,write:hello!
read: Illegal seek rc=7,write:hello!
read: Illegal seek rc=7,write:hello!
read: Illegal seek rc=7,write:hello! 原程序意图:将文件hello1里的内容读出,并将此内容每隔10秒写到hello2里面
问题:1):为什么会出现read: Success?? 2):为什么会出现read: Illegal seek??? |